On stardate 3018, DeSalle was placed in command of the Enterprise while the rest of the senior staff (including the captain, first officer, chief engineer, and the helmsman) were off the ship, and spearheaded an effort to pierce an alien barrier, which had been erected by Korob to prevent the Enterprise from sending help to a landing party that was trapped on Pyris VII. The Enterprise crew were close to escaping the field when Korob removed it himself, as part of his effort to help the Starfleet explorers escape Sylvia's attention. (TOS: "Catspaw")

DeSalle's first name is not established on-screen but was given as "Vincent" in a cast list that was written for the final draft script of "The Squire of Gothos", dated 26 October1966. The main body of the script described the character as follows: "Navigator Vincent De Salle – a tall, strong featured man." He was also listed as having that first name in Bjo Trimble's Star Trek Concordance; Trimble directly used many of the episode scripts in compiling her work. The FASACadet's Orientation Sourcebook remained true to the given name "Vincent" as well.

The script of "This Side of Paradise" referred to the character as "Lieutenant Timothy Fletcher". However, when Michael Barrier was cast in the role, the production staff realized he had previously played a character named "DeSalle" in "The Squire of Gothos", and changed the name accordingly. This explains why DeSalle was a navigator in the earlier episode, while he is a science officer in the later installment (and yet still wearing a gold uniform). [1]

DeSalle's promotion to assistant chief engineer and his change in uniform color in "Catspaw" was devised by Gene Coon. Since Scotty was in command of the bridge whenever both Kirk and Spock were on an away mission, Coon figured they would need someone in charge of engineering during these occasions. He intended to make DeSalle a recurring character. However, as incoming scripts didn't feature any interaction between the bridge and main engineering in such situations, this was finally abandoned. (These Are the Voyages: TOS Season Two) According to the "Catspaw" script notes (27 April1967), "Assistant Chief Engineer DeSalle", was described as "a strong, capable man cast in the same general mold as Scotty, Uhura, Chekov, and the rest of the standard command crew"